I believe energy is not released during the reduction of NAD, but it does not make sense to me because I am of strong belief that all redox reactions are exergonic. For example the reduction of oxygen molecules following the oxidation of glucose releases a lot of energy. is the reduction of NAD a special case in which more energy is absorbed than released? And if it is a special case where more energy is absorbed than released than this reaction can be deemed an endergonic reaction. subsequently endergonic reactions cannot occur without an exergonic reaction, so another question come about. What exergonic reaction fuels the energy needed for NAD to be reduced? and how?